Coherent Nanoprecipitates Research Articles

Excellent radiation resistance via enforced local non-directional He diffusion in a WTaCrV multicomponent alloy containing coherent ordered nanoprecipitates

We design and investigate a W15Ta15Cr35V35 (at.%) multicomponent alloy (MCA) with exceptional radiation resistance. The sintered WTaCrV alloy exhibits a body-centered cubic (BCC) matrix with dispersed coherent ordered nanoprecipitates. After ∼3-hour irradiation under 400 keV He+ at room temperature (RT) and 450°C with a fluence of 2 × 1017 ions/cm2, the irradiation hardening values of the MCA are about a quarter of those of pure tungsten counterparts irradiated at identical conditions. Besides, helium bubbles generated in the irradiated matrix of the MCA are much smaller, compared with those in the pure tungsten and other tungsten-rich alloys previously reported. The exceptional radiation resistance of the present WTaCrV alloy can be mainly attributed to two synergistic mechanisms. First, the high lattice distortion of the solid solution matrix promotes the local non-directional diffusion of irradiation defects, effectively suppressing the aggregation of irradiation defects and helium atoms along specific orientations. This facilitates more uniform nucleation of helium bubbles in the alloy matrix. Second, carbon was introduced during fast hot pressing sintering as interstitial solute to form carbon-rich coherent ordered nanoprecipitates. The carbon-vacancy complexes generated in the nanoprecipitates inhibit the nucleation and aggregation of helium atoms at the vacancies during He+ irradiation. The above two mechanisms synergistically enhance the resistance against He+ irradiation. This work thus demonstrates a design strategy for high radiation resistance alloys by introducing well-tuned ordered coherent nanoprecipitates in multicomponent alloy systems.

Improving plasticity by Si-addition-induced coherent nanoprecipitates in Cu–Al–Mn alloy fabricated by laser powder bed fusion

In this paper, the Cu-10.8Al-8.3Mn-0.37Si alloy containing Mn5Si3 phase was obtained by adding Si element to the Cu-10.8Al-8.3Mn alloy. The two alloys were printed by laser powder bed fusion. The changes in the organization and tensile properties of the alloys and the mechanism were investigated. After Si addition, the Mn5Si3 nano phase precipitated in the alloy in addition to the β1 austenite phase. The Mn5Si3 phase was co-lattice with the β1 phase with an average size of 10 nm and was diffusely distributed. Standard tensile experiments showed that the yield strength of the Cu-10.8Al-8.3Mn-0.37Si alloy decreased by 57.7% and the elongation increased by 266% compared to the Cu-10.8Al-8.3Mn alloy, while the tensile strength remained essentially unchanged. The presence of Mn5Si3 phase provided nucleation points for martensite and promoted the generation of stress-induced martensite. Hence the yield strength was reduced. TEM results showed that the β1 phase in the Cu-10.8Al-8.3Mn-0.37Si alloy was fully transformed into stress-induced martensite after deformation, which displayed the transformation induced plasticity effect and hindered the slip of dislocations. Meanwhile, the Mn5Si3 phase was sheared by the stacking faults, which promoted the accumulation of hetero-deformation-induced stress. Therefore, the hardening capacity and plasticity of the Cu-10.8Al-8.3Mn-0.37Si alloy were enhanced. This work provides a new idea for the plasticity enhancement of Cu–Al–Mn-based shape memory alloys achieved by co-lattice nano-precipitated phase strengthening.

Effect of Coherent Nanoprecipitate on Strain Hardening of Al Alloys: Breaking through the Strength-Ductility Trade-Off.

So-called strength-ductility trade-off is usually an inevitable scenario in precipitation-strengthened alloys. To address this challenge, high-density coherent nanoprecipitates (CNPs) as a microstructure effectively promote ductility though multiple interactions between CNPs and dislocations (i.e., coherency, order, or Orowan mechanism). Although some strain hardening theories have been reported for individual strengthening, how to increase, artificially and quantitatively, the ductility arising from cooperative strengthening due to the multiple interactions has not been realized. Accordingly, a dislocation-based theoretical framework for strain hardening is constructed in terms of irreversible thermodynamics, where nucleation, gliding, and annihilation arising from dislocations have been integrated, so that the cooperative strengthening can be treated through thermodynamic driving force ∆G and the kinetic energy barrier. Further combined with synchrotron high-energy X-ray diffraction, the current model is verified. Following the modeling, the yield stress σy is proved to be correlated with the modified strengthening mechanism, whereas the necking strain εn is shown to depend on the evolving dislocation density and, essentially, the enhanced activation volume. A criterion of high ∆G-high generalized stability is proposed to guarantee the volume fraction of CNPs improving σy and the radius of CNPs accelerating εn. This strategy of breaking the strength-ductility trade-off phenomena by controlling the cooperative strengthening can be generalized to designing metallic structured materials.

Strong and ductile Resinvar alloys with temperature- and time-independent resistivity

Materials with well-defined electrical resistivity that does not change with temperature or time are important in robotics, communication and automation. However, the challenge of designing such materials has remained elusive due to the temperature-dependent electron-phonon scattering. Moreover, resistive electrical conductors used in flexible and mobile systems under high mechanical loads must possess both high strength and ductility. Achieving such multi-properties presents a fundamental challenge. Here, we solve this problem by combining multicomponent alloy design with atomic-scale chemistry tuning. We term the resultant material ‘Resinvar’ alloy, due to its invariable resistivity (148 μΩ·cm) over wide temperature ranges from room temperature to 723 K. The alloy also has high tensile strength (948 MPa) at large tensile elongation (53%). The distorted lattice, chemical short-range order and ordered coherent nanoprecipitates in the material enable the invariant resistivity via promoting temperature-independent inelastic electron scattering, and contribute to the excellent strength-ductility synergy by manipulating dislocation slip.

Decoupling mechanical and chemical effects on energetics of coherent nanoprecipitates with interfacial segregation

Interfacial energetics for coherent interfaces are typically calculated using two key concepts: interfacial energy and coherency strain energy. Although these calculations are well-established in pristine systems, their direct application to doped systems often leads to inaccuracies. This is primarily because foreign solute atoms not only modify interfacial energetics but also introduce additional mechanical and chemical effects within the bulk phases. To address this, our study employs the PSTRESS tag in VASP to simulate equivalent lattice stresses induced by solute atoms without physically incorporating them. This novel approach allows us to isolate the doping energy caused by the solute atoms’ mechanical and chemical effects, thereby enhancing our understanding of the impacts of dopants solely on interfacial energetics. Furthermore, we extend the calculations of interfacial energy and coherency strain energy to doped interfaces, providing a precise and effective evaluation method for both bulk and interfacial energetics in doped systems.

Nanosized austenite and coherent nanoprecipitates making maraging steel strong and ductile

Here we report a microstructural design in maraging steel, which renders superior strength-ductility synergy by combining the advantages of transformation induced plasticity and dislocation cutting mechanisms, via an economic thermomechanical route suitable for industrial scale. It aims at innovating ductile maraging steel without conceding too much strength. Specifically, a high-strength maraging steel is first treated by cold-rolling and intercritical annealing, which leads to partial retransformation and precipitation of supersaturated needlelike/near-spherical B2-structured nanoparticles occurring simultaneously in dislocated α′-martensite matrix. The material is further optimized by peak-aging, yielding a desired microstructure, with nanosized γ-austenite (d‾γ ∼150 nm) dispersed in lath α′-martensite (d‾α′ ∼130 nm) with dense spherical B2-nanoprecipitates (d‾B2 ∼6.5 nm), i.e., an austenite-maraging structure with hierarchical heterogeneity at nanoscale. The yield strength is measured to be ∼1.65 GPa, which is largely retained as it combines boundary strengthening, dislocation strengthening and ordering strengthening of nanoprecipitates. Surprisingly, significant work hardening renders an ultimate strength even high up to ∼1.9 GPa and a decent ductility of ∼6–7%, twice that of conventional maraging steels. Interrupted microstructure examination unravels that it is the hierarchical microstructure heterogeneity-induced sequential activation of plasticity-enhancing mechanisms that confers such excellent deformability. At the stage soon after yielding (ε∼1.5–3%), deformation-induced transformation from metastable γ-austenite to α′-martensite imparts a significant strain hardening rate (Θ) up-turning. At the high strain stage (ε>3 %), multiple dislocations cutting through B2-nanoprecipitates promotes the interaction and accumulation of dislocations, thereby postponing Θ attenuation and prolonging ductility.

Hierarchical nanostructure stabilizing high content coherent nanoprecipitates in Al-Cr-Fe-Ni-V high-entropy alloy

High-density coherent nanoprecipitates have been widely introduced into the design of new structural materials to achieve a superior strength-ductility balance. However, the thermal instability of nanostructures limits their fabrication and application. In this study, we investigated the temporal evolution of nanoprecipitates in coherent nanoprecipitation-strengthened Al0.5Cr0.9FeNi2.5V0.2 high-entropy alloy during isothermal aging. When annealed at 600 °C for more than 100 h, we found that its nanoprecipitates were invariably stable, with no obvious changes occurring in terms of morphology and distribution. The excellent stability was mainly attributed to the restricted state of interface migration and diffusion owing to the hierarchical nanostructure. The Cr-enriched nano-lamellar BCC phase divided the Cr-depleted FCC(L12) matrix, forming barriers to long-range diffusion and resulting in a kinetically slow coarsening rate. As the nano-lamellar BCC phase spheroidized as the aging temperature increased to 700 °C, the diffusion barriers were destroyed. Remarkable coarsening occurred after that, which further verified the significant effect of the nano-lamellar BCC phase on the microstructural stability. These results provide a paradigm for designing alloys stabilized via hierarchical nanostructure, achieving good strength-ductility synergy while excellent thermal stability.

Achieving excellent strength-ductility synergy in (Co, Cr)58Ni30Mo6Al6 high entropy alloys by suppressing intermetallic compounds and introducing nanoprecipitates

Precipitation hardening serves as a viable mechanism to enhance the strength of high/medium entropy alloys (H/MEAs). The nature of precipitates in HEAs varies based on the composition of multiple principal elements. In order to further enhance the performance of HEAs across different applications, it becomes imperative to exercise control over phase synthesis and suppress the precipitation of detrimental phases. In this investigation, we propose a strategy for regulating the precipitation of the second phase in (Co, Cr)58Ni30Mo6Al6 (Co/Cr ratio = 1, 1.5, 2, 3) HEAs. Through precise adjustment of atomic ratios, the detrimental σ and μ phases are effectively restrained, while coherent nanoprecipitates are achieved through subsequent aging treatment. These fine nanoscale coherent phases alter the mode of dislocation slip, transforming planar slip into cross-slip, thereby providing a novel mechanism for the strengthening of the alloy. This controlled elimination and precipitation of phase contributes to a hierarchical improvement in the mechanical tensile properties. The aged HEA exhibits exceptional characteristics, including a strength of 1.3 GPa and 31% plasticity at 298 K (1.67 GPa and 40% at 77 K).

Tailoring nanoprecipitates to achieve ultrahigh strength (CoCrNi)94.5W3Ta2.5 medium-entropy alloys

Metallic materials with high mechanical performance are in constant demand by various engineering applications. However, most conventional strengthening mechanisms inevitably suffer from fiercely sacrificing ductility, which severely limits service safety of metallic alloys, especially under various harsh circumstances. In this work, a novel ultra-strong (CoCrNi)94.5W3Ta2.5 medium entropy alloy (MEA) with dual nanoprecipitates is successfully developed. By conducting multiple thermomechanical processes, not only quantities of coherent γ" nanoprecipitates with D022 superlattice are introduced, but also massive semi-coherent η nanoprecipitates with hexagonal D024 superlattice are reconstructed with appropriate sizes and distributions, meanwhile ultrafine grains are achieved, together enabling superior strength-ductility synergies. This MEA exhibits not only high tensile strength of about 1.7 GPa and ultimate elongation of 23.8 % at room temperature, but also ultra-high tensile strength of about 2.2 GPa and still sufficient ultimate elongation of 13.2 % at cryogenic temperature. In-depth microstructure characterization indicates that the nanoprecipitates are effective barriers to dislocation motion at the early stages of plastic deformation. Intriguingly, the slip and deformation twinning could be transmitted across the phase boundaries with increasing applied strain, ensuring both strength enhancement and plasticity maintenance. At cryogenic temperature, much more complex deformation mechanisms are activated, e.g., multiple slip systems and high-density deformation twins, facilitating even better mechanical properties. The design concept of strengthening materials via tailoring dual coherent nanoprecipitates may afford a paradigm to develop advanced metallic materials with ultrahigh strength.

Improving ductility by coherent nanoprecipitates in medium entropy alloy

Controlling precipitates in spatial density and size distribution is essential for tailoring the microstructure and mechanical properties through precipitation hardening. We herein obtained heterogeneous grain structures with coherent L12 nanoprecipitates in (CrCoNi)94Al4Ti2 medium entropy alloy (MEA) by annealing and aging. Additional pre-aging leads to a high spatial density and more random distribution nucleation sites of the coherent L12 nanoprecipitates. The pre-aging doubled the ductility without apparently sacrificing the strength. Transmission electron microscopy (TEM) revealed that, in pre-aged MEA, finely dispersed L12 nanoprecipitates with higher spatial density were sheared by dislocation, promoting planar slips, which favors geometrically necessary dislocations (GNDs) piling up to increased hetero-deformation-induced (HDI) stress and work-hardening. Stacking faults, Lomer-Cottrell locks, and 9R structures were formed in aged and pre-aged MEA after tensile deformation. The formation of these defects enormously enhanced strain hardening by blocking dislocation movements and accumulating dislocations. Moreover, a higher frequency of interactions between defects and coherent L12 nanoprecipitates can be observed in the pre-aged MEA due to the more randomly distributed L12 nanoprecipitates, substantially increasing ductility. This work demonstrates a new route to achieving a super strength-ductility combination of single-phase FCC high entropy alloys by nanoscale coherent precipitation strengthening.

Excellent combination of strength, conductivity and ductility realized in a dilute Cu-Cr-Zr alloy by coherent nanoprecipitates

Here, by a proper design of chemical composition to provide a guarantee of excellent conductivity and high enough strength, a new dilute Cu-Cr-Zr alloy is developed. The alloy, after two-stage heavy cold rolling and subsequent aging, consists of high-density coherent or semi-coherent nanoprecipitates and exhibits a yield strength of over 600 MPa, uniform elongation about 9.0%, and conductivity about 90% IACS.

Hierarchical structured Zn-Cu-Li alloy with high strength and ductility and its deformation mechanisms

Although Zn-based alloys exhibit great potential as biodegradable implants due to their moderate degradation rate and acceptable biocompatibility, the mechanical property is insufficient to meet medical applications. In this study, a Zn-2Cu-0.8Li (wt%) alloy with both high strength and high ductility is developed via a unique hierarchical structure. The alloy is composed of a hard micron-sized β-LiZn4 matrix, a soft submicron η-Zn phase and dispersive ε-CuZn4 nanoprecipitates. The ε-CuZn4 nanoprecipitates grow along the specific direction and exhibit a coherent interface with the matrix. During the room-temperature tensile deformation, continuous dynamic recrystallization (CDRX) related to dislocation absorption and preferential misorientation increase near grain boundaries, as well as 〈c + a〉 dislocations, are observed. The excellent strength of the alloy is mainly attributed to the hard β-LiZn4 matrix with fine grains and the dispersive ε-CuZn4 coherent nanoprecipitates. Simultaneously, favorable ductility is ensured by the deformable matrix with fine grains, and further improved by the activated CDRX, 〈c + a〉 slip and soft submicron η-Zn phase. Owing to the unique hierarchical microstructure, Zn-2Cu-0.8Li alloy exhibits a yield strength of 426.2 MPa, ultimate tensile strength of 472.2 MPa, uniform elongation of 43.7% and fracture elongation of 63.7%, showing great prospects for broader biomedical applications. This research proposes a significant strategy for the design of Zn alloys with excellent combination of high strength and ductility.

Ab-initio study on electronic, mechanical and dynamical properties of maraging steel containing coherent B2 type (Fe, Al)Ni nanoprecipitates

The ultrastrong maraging steel containing coherent B2 type (Fe, Al)Ni nanoprecipitates possesses outstanding strength and ductility with the potential to meet the demands in aerospace, advanced energy, etc. However, its transport properties including electrical and thermal conductivities have not been systematically studied. Based on the first-principles calculations, a model of Fe-7 at%(Fe, Al)Ni alloy containing B2 type (Fe, Al)Ni coherent nanoprecipitates was constructed, and its electronic, mechanical, and dynamical properties were calculated. The results showed that its bulk modulus is 169.6 GPa and the Poisson's ratio is 0.31, which are consistent with the experimental strength and ductility reported in Nature before. In addition, its unfolding band structure and phonon dispersion spectrum prove that the ultrastrong steel also has good electrical and thermal conductivities theoretically, which is similar to that of pure Fe metal. The experimental results of electrical resistivity and thermal conductivity verify the correctness and accuracy of the calculations.

A novel high-entropy alloy with exceptional strength and elongation via bimodal grains and lamellar nano-precipitates

This study presents a new effective approach for enhanced mechanical properties of the high-entropy alloy (HEA) Al7.3Co21.3Cr10.7Ti4.9Fe21.3Ni32.0Cu2.5 obtained by cold-rolling of columnar grains and subsequent annealing. This processing strategy aims to construct a microstructure of bimodal grains and coherent lamellar nano-precipitates. An ultrahigh strength of ∼1.68 GPa and a high elongation of ∼13.5% after annealing at 700 °C for 4 h were obtained, which are superior to those of previously reported similar HEAs. The ultrahigh strength originates mainly from the lamellar nano-precipitates strengthening and the bimodal grain size; however, the large elongation correlates to a progressive work-hardening mechanism regulated by the collaborative deformation of the ultrafine grains and the coarse grains and the unique nano-lamellar precipitates. This study provides a new strategy to utilize bimodal grains and coherent nano-precipitates in the development of HEAs or other similar alloys.

Lightweight, ultrastrong and high thermal-stable eutectic high-entropy alloys for elevated-temperature applications

Eutectic high-entropy alloys (EHEAs) that combine the advantages of HEAs and eutectic alloys are promising candidates for high-temperature applications. However, currently developed EHEAs still exhibit high densities and low high-temperature strengths, which limit their usage. Here we propose a strategy to design lightweight, strong, and high thermal-stable EHEAs by introducing an extremely stable Heusler-type ordered phase (L21 phase) containing a high-content of low-density elements and constructing a low lattice misfit eutectic-phase interface, which can lead to generate ultrafine and stable lamellar structures and high-density of coherent nanoprecipitates. As a manifestation of this strategy, a novel bulk Al17Ni34Ti17V32 EHEA was designed to consist of L21 and body-centered-cubic (BCC) phases (interlamellar spacing ∼ 320 nm) with a lattice misfit only 2.4%. This alloy has one of the lowest densities (∼ 6.2 g/cm3) among all EHEAs reported previously and exhibits much higher high-temperature hardness and specific yield strengths than most reported refractory HEAs (RHEAs), lightweight HEAs (LWHEAs), EHEAs, and conventional superalloys. This work paves the way to develop light EHEAs with excellent high-temperature properties.

Improved strength-ductility synergy of directed energy deposited AZ31 magnesium alloy with cryogenic cooling mode

ABSTRACT Motivated by the effect of cooling rate on microstructure, standard air cooling (AC) and novel cryogenic cooling (CC) were employed in the wire-arc directed energy deposition process of Mg-alloy. The influences of cooling modes on macrostructure, defects, microstructure, mechanical properties and deformation behaviour were systematically investigated. Compared with AC component, CC component exhibits improved performance with yield strength, ultimate tensile strength and elongation increased by 50%, 58% and 174%, respectively. The improved strength-ductility synergy can be attributed to the decreased porosity, profuse nano-precipitates, finer equiaxed grain within inter-layer and the transformation of columnar to equiaxed grain within intra-layer. The enhancement of strain hardening rate by highly coherent nano-precipitates impeding dislocations glide, dynamic Hall-Petch effect of multiple twins and numerous 3D obstacle networks of dislocations should be responsible for the significant elongation improvement. This study thus introduces new insights into defect alleviation, microstructure modification and performance enhancement of additive manufacturing Mg-alloys.

Precipitation behavior and microstructural evolution during thermo-mechanical processing of precipitation hardened Cu-Hf based alloys

A recently found precipitation hardened Cu-Hf alloy is a promising candidate for the fabrication of novel high strength and high electrical conductivity materials. However, the precipitation behavior and microstructural evolution during thermo-mechanical processing remain poorly recognized. The present paper focuses on the crystallography, thermodynamics and kinetics of precipitation process during isothermal aging and the interaction between nano-precipitates and nano-twins during liquid nitrogen temperature (LNT) rolling in Cu-Hf alloys. The isothermal aging precipitation procedure of Cu-Hf alloys was identified as supersaturated FCC-Cu → coherent Cu5Hf phase → incoherent Cu51Hf14 phase. The coherent Cu5Hf is oriented with respect to the Cu matrix: (111)Cu//(311)Cu5Hf, [0−11]Cu//[0−11]Cu5Hf. According to thermodynamic assessment and kinetic analysis, the formation of intermediate Cu5Hf phase is due to the lower accommodation energy and interfacial free energy of coherent nano-precipitates, and the change of the growth mode results in shape change in nano-precipitates. Based on molecular dynamics simulations, the significant improvement in the twinning ability of Cu-Hf alloys by the pre-existing nano-precipitates leads to the formation of plenty of nano-twin bundles during LNT-rolling. Finally, a new type of Cu-Hf based alloys with an excellent combination of high strength, high electrical conductivity, as well as high heat-resistance were fabricated by routine process.

Highly stable coherent nanoprecipitates via diffusion-dominated solute uptake and interstitial ordering.

Lightweight design strategies and advanced energy applications call for high-strength Al alloys that can serve in the 300‒400 °C temperature range. However, the present commercial high-strength Al alloys are limited to low-temperature applications of less than ~150 °C, because it is challenging to achieve coherent nanoprecipitates with both high thermal stability (preferentially associated with slow-diffusing solutes) and large volume fraction (mostly derived from high-solubility and fast-diffusing solutes). Here we demonstrate an interstitial solute stabilizing strategy to produce high-density, highly stable coherent nanoprecipitates (termed the V phase) in Sc-added Al-Cu-Mg-Ag alloys, enabling the Al alloys to reach an unprecedented creep resistance as well as exceptional tensile strength (~100 MPa) at 400 °C. The formation of the V phase, assembling slow-diffusing Sc and fast-diffusing Cu atoms, is triggered by coherent ledge-aided in situ phase transformation, with diffusion-dominated Sc uptake and self-organization into the interstitial ordering of early-precipitated Ω phase. We envisage that the ledge-mediated interaction between slow- and fast-diffusing atoms may pave the way for the stabilization of coherent nanoprecipitates towards advanced 400 °C-level light alloys, which could be readily adapted to large-scale industrial production.

Hydrogen embrittlement resistance of precipitation-hardened FeCoNiCr high entropy alloys

Precipitation-hardened high-entropy alloys (HEAs) with coherent nanoprecipitates are considered promising candidates for structural application as they have shown a unique combination of high strength and good ductility. Nevertheless, the hydrogen embrittlement resistance of this kind of alloy remains unclear, which prevents the precipitation-hardened HEAs from practical uses in the environment with existence of hydrogen. In this work, we systematically investigated the influences of hydrogen on the mechanical properties and deformation behavior of a series of Fe–Co–Ni–Cr precipitation-hardened HEAs. Our results demonstrated that the hydrogen penetrating into precipitation-hardened HEAs can enhance localized plastic deformation and cause stress concentration near the fracture, but the response of mechanical properties is closely related to the number of nanoprecipitates. In the precipitation-hardened HEAs with a proper amount of nanoprecipitates, the localized plastic deformation promoted the formation of deformation twinning which relieved stress concentration and enhanced the strength and ductility concurrently. In those with excessive nanoprecipitates, however, the fracture process was accelerated and hydrogen embrittlement occurred with decreased ductility due to the increased critical twinning stress resulted from the small interspaces between precipitates. Our findings are helpful not only for understanding the hydrogen embrittlement mechanism in complex alloys, but also for the future design of high-performance HEAs with good hydrogen embrittlement resistance.

Non-equilibrium time-temperature-transformation diagram for enhancing magnetostriction of Fe-Ga alloys

Coherent nanoprecipitates formed at early-stage decomposition in a number of body-centered-cubic (BCC) Fe-based alloys with nonmagnetic solute have been found to strengthen their magnetostriction significantly. Despite that the differences in structure and properties between equilibrium and metastable states have been well recognized in an extensively-studied system Fe-Ga, however, a non-equilibrium time-temperature-transformation (TTT) diagram for manipulating the intermediate nanoprecipitates towards further enhancing magnetostriction is still lacking. By systemically investigating the time- and temperature-dependent early-stage phase transformations of the magnetostriction-peak composition alloy Fe73Ga27, a non-equilibrium TTT diagram and the corresponding time-temperature-property (TTP) relation were successfully determined in this work. A nose temperature (the optimum temperature with maximal nucleation rate) of ∼400 °C to produce face-centered-tetragonal (FCT) L60 nanoprecipitates was determined in the diagram. Above the nose temperature, the L60 nanoprecipitates grow much faster and become incoherent rapidly, characterized by their enlarged tetragonality c/a towards the equilibrium face-centered-cubic (FCC) L12 phase. Below the nose temperature, the L60 nanoprecipitates grow much slower and keep coherent with the BCC matrix over a wide aging time range, but the low atomic diffusion rate and the coherent elastic energy produce extra hexagonal omega nanoprecipitates at the phase transformation front. Based on the non-equilibrium TTT diagram, the optimally-aged random polycrystalline alloy with coherent, dense and fine L60 nanoprecipitates can exhibit magnetostriction as large as 180 ppm, nearly 3 times of that of the solution-treated counterpart. Consequently, this work not only provides a processing base for enhancing magnetostriction of Fe-Ga alloys, but also may offer important guidance to tailor the microstructure of other nanoprecipitates-bearing alloys with similar diffusion-controlled phase transformation.